Method of reducing the viscosity characteristics of nitrocellulose



" characteristics.

Patented Dec. 8, 1925.

UNITED STATES PATENT OFFICE.

NEIL S. KOCHER AND VICTOR E. KIMMEL, OF ROCHESTER, NEW YORK,ASSIGNORS'TO EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YORK, ACORPORATION OF NEW YORK.

METHOD OF REDUCING THE VISCOSITY CHARACTERISTICS OF NITROCELL'ULOSE.

No Drawing. I

To all whom it may concern:

Be it known that we, NEIL S. KooHnR and XTICTORVE. KIMMEL, citizens ofthe United States of America, residing at Rochester, in the county ofMonroe and State of New York, have invented certain new and usefulImprovements in Methods of Reducing the Viscosity Characteristics ofNitrocellulose, of which the following is a full, clear, and exactspecification.

This invention relates to processes for treating introcellulosicmaterials in orderto lower the viscosity characteristics of thenitrocellulose. One object of the invention is to provide a process forlowering the viscosity characteristics of the nitrocellulose, which willbe safe, simple, and inexpensive. Another object ofthe invention is toprovide such a process in which the treatment will be under accuratecontrol, and in which the results may, therefore, be readily duplicated.Still another object of the invention is to provide a process which maybe carried out at atmospheric pressure without the necessity of specialpressure apparatus. Another object of the invention is to pro vide aprocess which may be carried outv at room temperature within areasonably short time Without the expense and trouble of heatingoperations. Other objects will hereinafter appear.

v For certain purposes there is a demand for solutions of nitrocellulosewhich are concentrated and yet spray easily,that is, they have a highpercentage of nitrocellulose in them, but have a low viscosity. Thekinds of nitrocellulose which are met with most frequently have highviscosity characteristics, and can not be formed into the abovementioned solutions without modification. Moreover, the kinds ofnitrocellulose which are present in pyroxylin waste and film scrap orother'sources of cheap waste material, have high viscosity It is,therefore, desirable to provide a safe, simple and cheap process forconverting such high viscosity types of nitrocellulose into those of lowviscosity characteristics, which can be used in the above mentionedspraying operations.

We have found that the viscosity characteristics of nitrocellulosicmaterial may be usefully lowered for this purpose, by treating it withan acid solution of a chlorate Application filed February. 25, 1925.Serial No. 11,591.

of an alkali metal, such forexample, as otassium chlorate. The treatmentispre erably conducted at atmospheric pressure, and at room temperature.While heating will accelerate the action, it is preferable to proceed atroom temperature, the action being sufficiently rapid for practicalpurposes. This treatment is applicable to nitrocellu lose in variousforms, such as in the form of original nitrated cellulose fibers, or inthe form of colloidized products such as solid colloidized film scrap,and pyroxylin waste. The nitrocellulose may be associated or not withsofteners or high-boiling organic compounds like camphor, butylalcoholand etc. \Ve shall now give a specific exam le of one applicationof our understood that the inventionis in no way restricted to thedetails thereof except as indicated in the appended claims.

The nitrocellulose material, such as pyroxylin waste, or film scrap fromwhich the gelatinous coatings have been removed, is treated in a bath ofstrong mineral acid containing a small amount of potassium chlorate. Thematerial is preferably comminuted so as to expose a large area, relativeto its mass, thus promoting a uniform action throughout the Whole of it.The pieces of material are preferably kept covered with the solutionduring the treatment. One bath which We have found useful is an aqueoussolution of hydrochloric acid containing approximately 36% of thelatter, and also containing about one-tenth of one per cent of potassiumchlorate. Another equally suitable bath is a solution of nitric acid inwater of approximately 65% strength, and likewise containing aboutonetenth of one per cent of potassium or sodium chlorate.

The duration of the treatment varies, and the time to end it ispreferably determined by tests. Representative samples of material aretaken from time to time, washed,

reduction in viscosity, the process will likewise be' shortened.Consequently, when working at room temperature, we may vary the durationof treatment from a few hours to several days. In the above examples wemay substitute original nitrated cotton fibers instead of colloidizednitrocellulosic materials. The concentrations of the acids may also bereduced, but we prefer to work with strong solutions, as indicatedabove.

During the action, a mild denitration may take )lace, but the reductionin viscosity reaches the desired state before the denitration hasproceeded to a harmful extent. In general we do not prefer to reduce thepercentage of the nitrogen in the nitrocellulose below 9.5%. \Vhen itproceeds by Letters Patent is:

1. The process of treating nitrocellulosic material, which comprisesacting thereon with a solution of mineral acid containing a chlorate ofan alkali metal until the viscosity characteristics of thenitrocellulose are reduced, the action being stopped before denitrationof the nitrocellulose reduces its nitrogen content below 2. The processof treating nitrocellulosic material, which comprises acting thereonwith a concentrated aqueous solution of vmineral acid containing lessthan one per cent of chlorate of an alkali metal, until the viscositycharacteristics of the nitrocellulose are reduced, the action beingstopped be fore denitration reduces the percentage of nitrogen in thenitrocellulose below 9.5%.

3. The process of treating nitrocellulosic material, which comprisesacting thereon with a concentrated aqueous solution of hydrochloric acidcontaining less than one per cent of potassium chlorate, the actionbeing stopped before denitration impairs the solubility of thenitrocellulose.

4c. The process of treating solid colloidal nitrocellulose associatedwith a high-boiling organic compound, which comprises immersing saidnitrocellulose in a bath containing a strong aqueous solution of mineralacid and potassium chlorate, the action being stopped before denitrationreduces the nitrogen in the nitrocellulose below 9.5%.

5. The process of treating solid colloidized nitrocellulose associatedwith a highboiling organic compound, which comprises immersing the samein a concentrated aqueous bath of mineral acid containing one tenth ofone per cent of potassium chlorate, the action being stopped beforedenitration reduces the percentage of nitrogen in the nitrocellulosebelow 9.5%.

6. The process of treating nitrocellulosic materials containingnitrocellulose mixed with a high-boiling organic compound,-

which comprises immersing the same in a bath containing a solution ofmineral acid of more than 30% strength, said bath containing less thanone per cent of the chlorate of an alkali metal, the action beingstopped before the percentage of nitrogen is reduced below 9.5% in thenitrocellulose.

7. The process of treating solid colloidizod nitrocellulose whichcomprises acting on the same with 36% hydrochloric acid bath containingone-tenth of one per cent of potassium chlorate, the action beingmaintained until the viscosity characteristics of the nitrocellulose arereduced, but being stopped before the percentage of nitrogen in thenitrocellulose is reduced below Signed at Rochester, New York, this 30thday of January, 1925.

NEIL S. KOCHER, VICTOR E. KIMMEL.

